1. Field
The present disclosure generally relates to a chip package for semiconductor dies or chips. More specifically, the present disclosure relates to a chip package that includes an interconnect with a multilayer electroplated stack that has an initial melting temperature to form a bump that is different from a subsequent melting temperature to reflow the bump during package assembly.
2. Related Art
An increasingly popular technique to increase the functionality per unit volume in a system is to heterogeneously integrate chips built on different technology platforms (such as digital, photonics, MEMS, analog circuits, mixed-signal circuits, radio-frequency circuits, etc.) onto a common substrate and package platform in which the chips are arranged and stacked in three dimensions. Assembling such a system often involves a step-wise technique in which the individual chips are put together. For example, a flip-chip bonding technique may be used to maximize the number of connections at the interfaces between the chips.
Flip-chip bonding is typically achieved using a thermocompression or reflow technique. In systems in which chips are flip-chip bonded to other chips, and then multiple chips are flip-chip bonded to a common substrate, there may be multiple different flip-chip bonding operations. Because the flip-chip bonding operations usually involve the use of high-temperature processing, it is often important that pre-attached components are not harmed by subsequent or downstream reflow operations. For example, if a first flip-chip bond is between a first chip and an interposer, then a subsequent reflow/attachment technique between the interposer and the common (package) substrate should not degrade the quality interconnection between the first chip and the interposer. However, existing solder bumps and, more generally, interconnects often can be degraded by subsequent thermal processing, which poses a challenge to integrated multiple chips on a common substrate in a system.
Hence, what is needed is a chip package without the above-described problems.